Weighing system



Jul 27, 1943.

- MIQTATEI WEIGHING SYSTEM- Filed Feb. 5, 1940 ,5 Sheets-Sheet 1 INVENTOR MALCOLM G. TATE II /1 I S IIIIIIIIIIIIIIIIUIIIIIIIIIII Ill Jul 21, 1943.

' M. c. TATE 2,325,345

WEIGHING SYSTEM Fi led Feb. 5, 1940 5 Sheets-Sheet 2 INVENTOR MALCOLM C. THTE ATTORNEY July 27, 1943. M. c. TATE WEIGHING SYSTEM Filed Feb. 5, 1940 5 SheetsSheet 3 INVENTOR MALCOLM G. TATE I I A'ITORN July 27, 1943. M. c. TATE WEIGHING SYSTEM Filed Feb. 5, 1940 5 Sheets-Sheet 4 M r gg ii WV liigfia INVENTOR A'TTORN E v LCOLM G. TATE B July 27, 194.3. M. c. TATE ,3

' WEIGHING SYSTEM Filed F8b.'5, 1940 5 Sheets-Sheet 5 sad 7 F INVENTOR MALCOLM C. TnTE Patented July 27, 1943 UNITED-STATES PATENT OFF IGE WEIGHING SYSTEM Malcolm C. Tate, Stamford, Conn, assignor to The Baldwin Locomotive Works, a

of Pennsylvania corporation Application February 5, 1940, Serial No. 317,286

. 28 Claims.

This invention relates generally to apparatus for measuring and/or indicating certain conditions to which the apparatus. is responsive and relates more particularly to a load weighing and indicating apparatus and system for materials testing machines.

While my invention is illustrated herein as being specifically applicable to weighing hydraulic forces such as are utilized in various types of hydraulically operated materials testing machines, yet it will be understood that various features and principles of operation can be utilized to measure,

indicate and/or control certain conditionssuch I as load, temperature, etc. created in various-manners. However, in the field of materials testing machines a great many problems are peculiar thereto because a materials testing machine is fundamentally a cientific precision instrument having the peculiar requirement that notwithstanding its scientific precision qualities still it must be a rugged piece of machinery adapted to withstand tremendous forces. Also the forces to be measured vary through a wide range and yet it is most essential that the apparatus be just as sensitive, accurate and responsive in the low load ranges as in the higher load ranges.

It is an object of my invention to provide an improved load weighing apparatus that is rugged necessary extraneous5 retarding forces; to profor equipment of its class and yet is flexible in its manipulation and accomplishes the several precision qualities of sensitivity, accuracy and remanner. a

A further object is to provide an improved air controlled load weighing apparatus which in one an improved simplified air jet and baille system employing a relatively large constant pressure orifice in cooperation with a large size jet opening thereby obtaining a very high degree of sensitivity, accuracy and responsiveness without the need of any interposed devices for magnifying the pressure changes occurring in the air system.

- A-further object is to provide an improved multiple load range weighing and indicating system adapted to be changed in a simple and direct manner from one load range to another without sponsiveness in a simple, positive and direct specific aspect of the invention is accomplished by any possibility of damage to the apparatus or of v interruption to the progress of a test thereby permitting a testing operation to be made with maximum dispatch together with retaining the several precision qualities heretofore mentioned.

A further object is to provide an improved multiple load weighing and indicating system whereby the zero point for each load range may be accurately and expeditiously established prior to starting a test.

A further object is to provide improved means for transmitting a load measurement from the weighing apparatus to an external source such as a recorder or any other desired instrument.

A more specific object in this respect is to provide improved means for changing the magnification of the measurement to be transmitted.

Other objects are to provide an improved arrangement for maintaining the weighing and operating forces preferably in axial alignment to I avoid introductionof bending moments or other disturbing factors into the weighing system; to provide an improved arrangement for damping vibrations which might occur in the Bourdon tubes or the control mechanism but at the same time avoid introduction of friction or other unvide an improved arrangement for preventing overstressing of the low range Bourdon tube but without interfering with the action of the high range Bourdon tube although insuring adequate protection of the high range tube against sudden release of large load pressures such as occur upon rupture of a specimen; to provide an improved air control and also spring operation of a servomotor whereby the servo-motor has a desired extent of stroke in response to a minimum pressure change in the Bourdon tube; and to provide a ings in which:

Fig. l is a front elevation of a load indicating dial forming a part of my improved combination;

Fig. 2 is a transverse sectional view taken substantially on the line 22 of Fig. 1;

Fig. 3 is a perspective of the rear side of the dial mechanism showing the multiple load range weighing apparatus;

Fig. 4 is a rear view of the indicating dial and th load range adjusting and zero positioning means;

Fig. 5 is an enlarged view of the high load range Bourdon tube and the Jet-baffle therefor together and crosshead 8.

with a section of the baffle dampener taken stantially on the line -501 Fig. 3;

Fig. 6 is an enlarged transverse sectional view of the mechanism taken substantially on the line 56 of Fig. 3 whereby the recorder or other extraneous apparatus is operated with various degrees of magnification by the load weighing mechanism;

Fig. 6a is a horizontal section taken on the line tc$a of Fig. 6;

Fig. 6b is a vertical section taken substantially on the line tb-tb of Fig. 6;

Fig. 7 is a horizontal section taken substantially on the line l? of Fig. 6;

Fig. 8 is an enlarged transverse section taken on the line 8-8 of Fig. 3;

Fig. 9 is a diagrammatic outline oi certain load weighting elements employed in my improved combination;

Fig. 10 is a horizontalsection taken substantially on the line id-iil of Figs. 3 and 9; and

Fig. ll. is a sectional view taken on a plane corresponding to line iili of Fig. 9.

In the particular embodiment of the invention such as is disclosed herein merely for the purpose of illustrating one specific 'form among possubsible others that the invention might take in.

practice, I employ certain fundamental elements constituting the subject, matter of my Patent No. 2,212,085, filed January 27, 1936. However, because certain of these elements are involved in a new cooperative relation in the combination constituting the present invention the same will be fully described herein. As shown in Fig. l, the

' dial 1 has two sets of'load graduations 2 and 2' adapted to be rendered selectively visible through a slotted mask 3 coaxially disposed in superimposed relation to the dial.

A load indicating pointer i is suitably Journalled in a bearing 5, Fig. 2, and is provided at its rear end with a pinion 6, Fig. 9, to be operated by a vertically movable rack i pivotally secured at its lower end to a vertically movable crosshead 8, Fig. 3. A rod 9, Fig. 6, extends downwardly through a vertical stationary'bearing bracket IQ for connection to an air controlled servo-motor i I specifically in the form of a bellows whose lower end is secured to a suitable stationary base 52, Fig. 3, and whose upper ,endis movable vertically to actuate rod 9 The support it has at each of its upper. and lower ends sets of three. roller bearings generally indicated at-fl3 for guiding rod I 9 with minimum friction. A pair of bolts it, Fig.

6, rigidly holdbearing bracket Hi to a stationary back plate a of the dial structure.

The crosshead 8, Fig. 3, is also connected through a pair of side rods IE to a set of springs generally indicated at B6. and i l whose upper ends are connected to across bar I B pivotally supported as at l9 to a suitable bracket which is v clamped by'a bolt and nut 20, Fig. 5, to the free closed end or a high load range Bourdon tube 2|. The fixed end of this Bourdon tube is suitably secured in a bracket 22 secured to backing plate l5a while a pipe 23 is connected to a source of hydraulic pressure of a materials testing machine such as the main hydraulic loading cylinder or to the hydraulic support, of an Emery type machine shown, for example, inPatent masses 'or to any other desired source of pressure.

The c'rosshead 8 is further connected, Fig. 3, through a rod '26 rigidly secured to the crosshead and through an adjustably threaded stem ii, to a low load range set of springs generally indicated at 28. The upper ends of this set of springs are pivotally connected as at 29 to a closure bracket 30 of a low load range Bourdon tube 3!. The fixed end of this Bourdon tube is secured to the backing plate l5a through a bracket 32 and is connected by a pipe 33 to the same pressure source as pipe 23, preferably by a common connection. The closure brackets 29 and 3B are identical and also the sets of springs are of the isoelastic type having a straight line stress-strain relation although the set of springs 28 is of smaller capacity than the springs it, i? so asto produce the desired ratio between the two load ranges.

To provide a simple and effective arrangement for preventing rotation oi crosshead A, two rods 35 are individually rotatably adjustably mounted in a laterally onset boss 3? formed integrally with crosshead t. The two outer ends of these rods have eccentric portions 36c, Fig. 10, upon which is mounted a pair of roller bearings 36' adapted to have rolling engagement with the rear surface of backing plate 35a.v These rods may be adjustably rotated to establish said surface guiding contact through the action oithe eccentric portions 3% and after the adjustment is made suitable set screws inboss 3?. may firmly hold the rods in position. The individual adjustability or the rods as gives greater latitude of adjustment than if only one continuous rod were used.

As shown in Figs. 3 and 9 a pair of servo-motor springs 38 and 39 of substantial length are secured at their lower ends to frame i2 and at'their upper numbers for the lowload range elements will be primed. As shown in Fig. 5, the Bourdon tube bracketZfi has an elongated inflexible arm 63 carrying a flexible bafile plate M which is rigidly secured at its inner end to arm 58 while its outerend overlies an air Jet 66. A screw 46 carried by arm 63 is adapted to adjust the vertical position of bafile plate 36. The jet 45 is rigidly supported in a suitable bracket ti secured to the backing plate lEa. Also secured to arm 43 is a damping plate 48 disposed in a stationary oil chamber 49 mounted on backing plate 55a. A novel characteristicof damping plate 68 is that it does not act as a dashpot but instead merely obtains its damping action byvirtue of the inertia of the damping liquid, it being noted that the plate &8 is widely spaced from the walls or container 69.

This provides a very stable action for the hams. zit without influencing the accuracy, sensitivity or responsiveness of the weighing operation.

The air jets t5 and 65' are respectively con nected, Fig. 9, through a pair of pipes 5d and hi to a load range shifting valve 52 adapted to selectively connect said pipes to the servo-motor H as by a pipe 53.. An air reservoir 5!; is in continuous communication with pipe 53 thereby insuring smooth operation of the bellows H. Air is supplied from any suitable source under a, pressure of upwards of 30 or 40 pounds through a pipe 55 and valve 55 to e. suitable air filter 57 and thence through a valve 5% for reducing the square inch on the outlet side which communicates with a control orifice 59 and thence with both the servo-motor and the selected jet. It will be noted that the air jets; orifices 58 and servo-motor are all connected together in a simple and direct manner without any interposed operating elements. Said direct connection is continuous at all times for a given load range, thatis, so. long as that range is operative. 'During operation of one range, the other range is inoperative.

Heretofore a relay valve was interposed in the air circuit so as to give a step-up of sensitivity. The openings in the jets and orifices of this prior arrangement were relatively small whereas my presentimproved combination obtains not only a high degree of sensitivity but does so with relatively large openings in the Jet and orifice 53. This feature, aided by the fact that the servomotor permits sufilcient stroke with a practically constant acting area, produces a combination wherein the servo-motor gives the desired stroke with minimum change in jet pressure (or baflie motion). This means that the jet-bailie distance tion is obtained between the downward force exerted by servo-motor springs 38 and 39 and the combined upward forces of the fluid acting in the servo-motor H and in the Bourdon tube 3|. During this operation the servo-motor H has a relatively large increment of movement I compared to a relatively small minute increment of movement of baiiie 84', this being accomplished by reason of the elasticity of spring 28. The relatively large movement of the servo-motor and crosshead 8 in turn transmit a corresponding degree of movement to rack l and pinion 6 thereby rotating the load indicating pointer 4.

Upon a decrease of load Bourdon tube 3| will contract thereby causing baiiie 44' to move toward jet 45' to restrict discharge of air from the jet. This increases the pressure in pipes 5|, 53 and in the servo-motor I thereby moving the servo-motor and crosshead 8 upwardly so as to reduce the tension on springs 28 whereupon baiile 44' will move very slightly away from the jet 45"to establish a balance between the downward force of servo-motor springs 38 and 38 and will change very little between zero load and full baiile motion is required to operate the servomotor and, therefore, the servo-motor will respond to very minute pressure ,changes in the Bourdon tube. (b) If the jet-orifice-servo-motor combination is highly sensitive as above pointed out, it means that an instantaneous pressure change in the tube of a given magnitude (producing instantaneous baflle motion) will tend to produce quick balancing of the system. (c) If the jet-servo-motor combination is highly sensitive as above pointed out, an external friction force (which might disturb the action of the servo-motor) will produce less disturbance in the stroke of the servo-motor (such as dial indication). In other words, the indicator or other external mechanism operated by the servo-motor the combined forces of the pressure acting upwardly in the servo-motor and in the Bourdon tube 3|. Of course, it will be iinderstood that the foregoing increase or decrease of load in Bourdon tube 31 may be continuously varied without interruption as during testing of a specimen and hence the foregoing balancing of forces will be a continuous operation, although where a test is maintained in a static condition the forego-' ing balanced forces will reach a corresponding static condition.

As described in my Patent No. 2,212,085, filed January 27, 1936, the Bourdon tubes are preferwill be better able to overcome outside friction sure valve 58 and thence through orifice 58 to Jet 45' and to servo-motor ll. Assuming that load is now applied to the testing machine, the Bourdon tube 3| will expand thereby raising baffle 44' minutely away from jet 45' to allow.

a greater rate of discharge of air through the jet. This results in a decrease of pressure in pipes 5l,.53 and servo-motor Ii. The springs 38 and 39 which are initially under tension hold down the cross-arm 40 so as to move crosshead 8 and rod 28 downwardly thereby pulling down the set of springs 28 to restore baiilell' substantially to its original relation to .jet 5. The baflle M is not moved to precisely its initial position but to a point where the pressure in pipe 5| will not be further reduced and hence a balanced relaably prestressed either hydraulically as by usual pre-loading springs fora hydraulic support in a materials testing machine or by an initial mechanical stressing of the tubes brought about by having the tubes, when in an unstressed and unloaded condition, initially expanded beyond their normal control position. Hence, when the tubes are assembled with the servo-motor mechanism the springs 38, 39 thereofwill mechanically pull the free end of the tube and accordingly contract the. same and stress its walls. Upon admission of air to the system the servomotor will move upwardly sufllciently only to bring the system into a balanced condition. The tubes however will retain sumcient prestressing so as to aid in the sensitivity of the system.

To change the load range capacity of the weighing apparatus, it is only necessary to rotate valve 52 in a clockwise direction so a to connect jet pipe 5|] with orifice 58 and the servomotor II. The operation of jet l5 and baiile M will then-be identical to the mode of operation described for the low load range Bourdon tube and the associated jet. bailie therefor as heretofore described. The balanced relation between the jet 45 and baflle 48 i maintained by a smaller amount of movement of servo-motor ll than is the case for the low load range jetbaiile' f, 45'. This smaller movement can be brought about by the fact that springs 18 and II are stiffer than spring 28 or, as is preferred, the acting area of tube 2| and the stiffness of springs l6 and H are designed so that servomotor ii will move the load indicating hand a proportionately smaller distance than would be the case if the same degree of load change oc- V curred in the low range operation. Hence, for

a given load change in the high load range, servomotor H will move the load indicating hand a able with the outer free end of thetube when the pressure is above the normal range of thetube. The stop 3i has the function of converting the tube from acantilever beam to a two point supported beam which reduces the maximum bending-moment and the stresses in the tube when inoperative. The high load range tube 2| is provided with an inverted top 2| engageable, Fig. 5, with the under side of Bourdon tube arm 13 and is vertically adjustably supported by screws Zia on the backing plate iila. A stop identical in structure and purpose to 2| is also provided for Bourdon tube 3|. The function of stop 2| is that upon occurrence of a sudden release of pressure on a tube in use, the hydraulic resultant force acting on the tube decreases suddenly. However, theload of the iso-elastic springs l6, l! or 28 continues'so that the tube tip is pulled downwardly. This downward motion 7 might be enough to tilt the baffle 44 so that it would not cover the jet 45 effectually. That is,

the bailie 44 might be canted diagonally across the jet opening whereas it is desired to have the baflle extend horizontally across the let. In fact, if the baffle is canted it would hinder and perhaps prevent the indication of the lower load values of this particular range. Hence, the stop 2| is set just below the normal operating position of the tube. If the tube now moves downward, it can only go down a very small distance, but sufiicient to firmly close the jet. The elements in the air system are also protected by a suitable relief valve 60 secured to and movable withthe upper movable end of the servo-motor II. The air pipe 53 has a flexible portion connected to the bellows so that it may easily move with the servo-motor.

Shifting of multi-load range indicating mechanism'gind establishment of zero positions thereof for r inactive ranges.As previously'mentioned the dial I has two sets of 'graduations 2 and 2' angularly offset with respect to each other, equal spacing of the graduations on the respective sets representing different unit load values which are proportionately related to the force elongation characteristics of the two sets of load weighingsprings 28 and l6, II. The two sets of dial gradnation have their own zero positions afigularly housing ll preferably extends above and-then turns downwardly at it; for connection to support 13 thereby allowing efiective rotation of the upper end 14 of housing ,li with the dial. Mask lever m is pivotally connected to plate lie by a pin and slot connection it, while the outer'end of said lever is pivotally connected at E6 to the rear side of mask '3 through a suitable bracket ofiset from each other in the manner shown in vice versa. Toeflect mask rotation and also to ll mounted thereon. The bracket 11 extends through a suitableelongatedopening I8 of the dial plate; Two different relative positions between the mask and disc are provided by a detent device having a roller arm is pivotally connected at one end to-bracket l1 and its other end has a detent roller receivable in one or the other of two V-notches 8t and 8! formed in 'a plate secured to the back of the dial and movable therewith. A. spring 82, secured at one of its ends to the dial l and at its other end to roller arm ls, insures a positive relative positioning of the dial and mask.

When the shifting valve 52 is rotated from one position to the other, lever 68 will cause wire 69 to move lever HI about its relatively fixed pivot 55 thereby causing pivot 16 to move bracket 11 and the mask 3 attached thereto. The roller detent will be received in either one of the V'- notches 80 or 8| so as to relatively'position the I the test, I have provided an improved combination whereby the correct zero position for each set of load dial graduations is established be,- iore the test starts. This is accomplished by setting the load weighing mechanism on the high load range under control of Bourdon tube 2|, Fig. 3, and then, without any load on the testing machine, rotating dial by a knob 84 on the front of the machine. This knob operates a series of gears 85, journalled in backing plate I5a, to move a gear rack 86 secured to the back of the dial. The dial is then rotated until its high load range zero position 81 is in alignment with the load indicating pointer 1.. The shifting valve 52 is then adjusted to place the load weighing mechanism on the low load range which is under the control of Bourdon tube 3|, Fig. 3. As before mentioned, the rotation of valve 52 causes valve stationary and the load, hand is moved until it is brought, into alignment-with thezero graduation 88. This adjustment is effected by varying the position of the jet-baiile control 44', 45", Fig. 3. To do this, the jet 45' is supported on a flexible plate 90 one end of which is secured to. a fixed bracket 9| projecting outwardly from the back of housing plate i511. This flexible plate is biased downwardly by a spring 92 while the free end of the plate, rests upon a small pointed rod 93 whose lower end is vertically guidedin a bracket 94 and actuated by a cam 95. This cam is rotated by a coordinate it with changes in the weighing ggyg- I tem from oneload range to the other,- I provide shifting valve 52, Fig. 4, having .a-lever 68 connected by a flexible wire 69 to an operating mask lever 70. The wire 69 is contained within a flexible housing "H secured at 12 to the backing plate Ilia while the other end of the cable is secured upwardlyior downwardly, as the case may be,

shaft 96 and a roller and gear 91, the roller shaft projecting forwardly through'the front panel 99 and provided. with a hand knob 98, Fig. 8. By rotating this knob the supporting rod 83 is moved thereby causing the same relative bafile-jet control action on the servo-motor as exists during expansion or contraction of the Bourdon tube.

Hence it is possible to manually control the servomotor and thereby through the rack I and pinion 6 adjust the position of the pointer lmuntil it is in alignment with the low load range zero position 08,.Fig. 4. This adjustment of the load hand does not destroy its relation to the zero position 81 of the high load range when the system is shifted'back to the high load range. This is because each load range involves its own preestablished relationship between its jet-baflie, the load hand and the dial. When the system is shifted to the low load range the jet-baflle of the high load range is rendered inoperative and vice versa when the system is shifted to the high load range. Hence it is possible to shift from one load range tothe other with complete certainty of having a correct zero position for each range. This permits a test to be started on the low load range with accurate indication of the load values and when the low load range capacity is about used up to then shift to the high load range without interrupting the test and with complete assurance that the high load value indications are correct.

Multiplying mechanism.To operate an external device such as the load responsive element of an autographic recorder, I have found that it is especially advantageous to have the rectiiinearly movable stylus actuated in proportion to the load and to rotate the usual recorder drum in response to strain of a specimen. Any usual and '7 a gear change mechanism having a stationary frame I00, Fig. 3, formed, as shown in Fig. 6, of front, intermediate and rear walls IOI, I02 and I03. The rear wall I03 is fastened by screws I04 to a flanged stud I05 which is secured as at I06 to the backing plate I5a. The stud I05 is offset to one side of the housing I0 through which the servo-motor rod 9 extends. As shown particularly in Fig. 7, the frame I00 has a pair of selectively operable pinions I 01 and N0 secured to a common shaft with a gear I09 which, in turn, drives a geared shaft IIO. This shaft has a roller gear I I I secured thereto for engaging, Figs. 3 and 6, a screw threaded normally nonrotatable shaft II2 which is held in engagement with the worm gear by a grooved roller H3 suitably iournalled on a bracket II 4 which is vertically adjustable on a red I I 5 projecting upwardly from as an integral part of rear frame wall I03. The threaded shaft II 2 has an extension 2' of any desired length extending to the external instrument to be operated. The relative relation between the shaft II2 and worm wheel I II may be adjusted merely by manually rotating threaded shaft II2 to the desired extent. The pinions I0! andI08 are-selectively engaged, Figs. 3 and 6, by a pair of gear racks I I6 and I I! each pivotally mounted as at H8 to a bracket vertically adjustably supported on a threaded shaft I I9 which is supported in a bracket I20, in turn, mounted on one of the servo-motor operated frame rods I5. Each gear rack has arms I22 and I23 rigidly formed therewith and providedwith hooks for selectively engaging a spring I24 whose upper end is mounted upon a suitable arm of bracket I20. The gear racks and arm I20 will, therefore, move vertically with the crosshead and servomotor thereby causing servo-motor movement to be transmitted to threaded rod H2 and in some multiplied proportion depending which rack H6 or II! is in mesh with pinions I01 or I08. The threaded shaft H2 and its extension II2 will move rectilinearly in a horizontal plane and it has been discovered that by attaching such a rod to the stylus of the recorder while the recorder drum is rotated in response to strain, it is possible to eliminate very serious difiiculties which have heretofore been incident to prior recorder operations wherein'the drum was rotated by the servomotor and the stylus was moved in response to strain. By the present arrangement the multiplying mechanism and stylus respond instantly and faithfully to every pressure change in the jet and orifice system without introducing any lag or inertia effects. Furthermore, the present gear arrangement is extremely simple, readily accessible and conveniently selective in its operation.

From the foregoing disclosure it is seen that I have provided a relatively simple, direct and positive-acting control system for the servo-mo-' --tor as well as providing a very effective multiload range weighing system which may be coordinated with the load indicating mechanism to insure accurate indication for either range as well as to permit a continuous testing operation through one load range into the next one. The apparatus effectively utilizes an inverted type of servo-motor wherein springs 38 and 39 of relatively great length actually rotate the load pointer during increasing loads under decreasing pressure within the servo-motor whereas increasing pressure within the servo-motor may cause the load pointer to indicate decreasing loads. Thi modeof operation is very effective in conjunction with the simple direct acting jet and orifice control wherein the servo-motor air pressure responds directly to the pressure variations in the jets. All of these features as well as others heretofore mentioned contribute to the high de--.

gree of sensitivity, accuracy and responsiveness of. the system herein disclosed.

It will of course be understood that various changes in details of construction and arrange-- ment of parts may be made by those skilled in the art without departing from the spirit of the invention as set forth in the appended claims.

I claim:

' 1. In combination, means movable in response to a change in a given condition, an air controlled power mechanism for causing said movable means to be moved oppositely to said responsive movement, relatively movable air jet and baflie elements one of which is moved with said re-. sponsive means, and an air supply passage having an orifice therein communicating at all times during normal operation directly with both said power mechanism and air jet whereby movement of said responsive means causes a variation in jet pressure which is transmitted directly to the power mechanism to cause it to move the responsive means in a contrary direction until a balanced relation exists between the servo-motor and responsive means.

2. The combination-set forth in claim 1 further characterized in that extensible means are inter- 3. The combination set forth in claim 1 further characterized in that said power mechanism has an expansible motor in which the air pressure vice versa and a spring for moving said motor upon reduction of pressure therein, whereby upon initial separation between said jet and bafile elements the air pressure in said motor decreases so that said spring moves said elements toward each other until a balanced condition is established and upon an initial movement of said elements toward each other the jet pressure increases so that said motor device moves under the influence of the increasedpressure to separate said elements until a balanced condition is established.

4. Hie combination set forth in claim 1 further characterized by the provision of an air chamber connected to said air supply passage at a point between said powermechanism and said orifice.

5. In combination, a plurality of movable condition responsive means operable for difierent ranges, air controlled power means for actuating a member in proportion to variations in the conditions, means for controlling said power means in accordance with one or the other of said responsive means including an air jet and baffle associated with each of said responsive means, an air supply passage having an orifice, means for selectively connecting one or the other of said jets with said power means, the selected jet and supply passage communicating at all times during normal operation directly with said power means whereby relative movement between the selected jet and its bafie effected by movement of the responsive means therefor causes variations in jet pressure to be transmitted directly to said power means to cause actuation thereof.

' 6. In combination, a plurality of condition rei sponslve means operable for different ranges, air

sponsive means, and an air supply passage having an orifice communicating directly with at least one of said jets and with said power means whereby variations in pressure of one of the jets occasioned by movement 01 its associated responsive means is transmitted directly to said power means to cause the same to re-establish said balanced relation of forces.

responsive means causes a variation in jet pressure which is transmitted directly to the power mechanism to cause movement thereof until said predetermined relation is established between said air jet and bailie elements. i

9. In combination, a pressure responsiveelemerit, an air controlled servo-motor controlled by said responsive element to balance the pressure force of said responsive element, yieldable means interposed between said servo-motor and said responsive element and connected to each of thesame whereby a relatively large servo-motor movement'takes place upon occurrence of an unbalance of the forces between said responsive element and said servo-motor, means forming a surface extending generally in the direction of movement of said servo-motor, and guiding means engaging said surface to prevent rotation of said yieldable means.

10. In combination, movable condition responsive means, an air controlled servo-motor for resisting movement of said responsive means, indicating means actuated by said servo-motor, means including air jet and bafiie elements one being normally fixed and the other being associated with said responsive means for movement therewith whereby relative movement between said jet and bafie varies the jet pressure thereby controlling said servo-motor so as to establish a balanced relation between the forces of said servo-motor andv said responsive means, and means for relatively adjusting said air jet and baiiie elements thereby to establish a predetermined balance of forces between said responsive means and servo-motor for creating a given initial position of said servo-motor and indicating means.

7. The combination set forth in claim 6 further characterized in that saidsupply passage communicates with a valve from which a plurality of air pipes communicate respectively with said jets, said valve havingprovision for connecting said air supply pipe selectively-with said jet pipes thereby rendering said responsive means selectively operable in accordance with whichever range is desired. I

8. In combination, movable condition responsive means, air jet and baflie elements one of which is connected. to said movable responsive means and the other of which is supported in a normal fixed position so that relative movement between said elements variably controls the jet pressure in accordance with movement of said responsive means, an air controlled power mechanism for moving said element which is connected to said responsive means so as to maintain a substantially predetermined relation between said elements, and an air supply passage having an orifice therein communicating at all times during 11. as combination .set forth in claim 10 rurther characterized in that said adjustable means includes a flexible plats upon which one of said elements is mounted and a ember having a pointed portion engaging said flexible member to efiect adjustments thereof.

12. In combination, a plurality of Bourdon tubes respectively adapted for different load ranges, power means forresisting movement of said tubes so as to establish a balanced relation of forces between'the power means andtubes, means responsive tochanges of pressure in said Bourdon tubes including air jet and bafile elements for each tube and means for selectively connecting one or the other of said jets to said power means for varying the pressure therein thereby to maintain said balanced forces after a change of pressure in the Bourdon tube which corresponds to the selected jet, and means whereby one of said Bourdon tubes is adapted upon completion of its load range to be converted from a cantilever into a two point supported beam thereby to limit the stresses set up in, said tube while the other tube remains operative under higher pressures during its load range.

13. In combination, a plurality of Bourdon tubes selectively operable for high and low load ranges, an air operated servo-motor for resisting movement of said Bourdon tubes to maintain a substantially balanced relation between the forces of the servo-motor and-Bourdon tubes, air jet and baflle elements associated with each of said tubes, means for rendering said tubes selectively operative to control pressure of said servo-motor and thereby to maintain said balanced forces upon occurrence of a change of pressure in the selected tube,v and means whereby the high load range, jet and baths elements are adapted to be main-- tained in an operative relation to each other upon occur'rence'oi a sudden decrease of load in the high load range tube.

14. The combination set forth in claim 13 further characterized in that said means for main taining the high load range air jet and baiile operative upon decreases of load comprises a stop for limiting relative movement between the jet and baiile-toward each other.

15. In combination, a multi-load range weigh- .ing mechanism, a multi-load range indicating mechanism having an indicating element common to each load range, said indicating element having one zero position for one load range and another zero position for another load range, means for shifting the indicating mechanism from one load range to another and holding the same in its shifted position, and means for relatively adjusting said indicating and load weighing mechanisms so as to establish correct zero positions for each of the load ranges before a load weighing operation is started whereby in shifting from one load range to the other the indicating mechanism will have a correct zero position as a base.

16. In combination, a multi-load range weighthe indicating mechanism will have a correct zero position as a base, and means for shifting the load range of one of said mechanisms and automatically shifting the other mechanism so that it has a corresponding load range.

17. In combination, load responsive means, an air operated servo-motor for resisting movement of said responsive means thereby to maintain a balanced relation of forces between the servomotor and responsive means, means for controlling said servo-motor in accordance with movement of said responsive means, and means for transmitting movement from said servo-motor to an extemalsource including a chain of gears having a worm wheel and a threaded rod engageable therewith, said rod being rectilinearly movable substantially tangentially to the worm wheel.

18. In combination, load responsive means, an air operated servo-motor for resisting movement of said responsive means thereby to maintain a balanced relation of forces between the servomotor and responsive means, means for controlling said servo-motor in accordance with movement of said responsive means, and means for transmitting movementfrom said servo-motor to an external source including a chain of gears having a pair oipinions of diiferent diameter and a pair of servo-motor operated racks-selectively engageable with said pinions.

19. In combination, a multi-load range weighing mechanism, a multi-load range indicating system having a load hand and a graduated dial provided with a plurality of sets of num bered load graduations each beginning with its own zero position, means for rendering the load ranges of theindicating system selectively operable, including a mask havinga series of openings adapted to uncover the graduations of only one set of graduations or the other, means for adjusting the load hand relative to one or said zero positions when the weighing mechanism is operative for one of its load ranges, and means for angular-1y moving said dial to adjust the same relative to the load hand for establishing the zero relation when the weighing mechanism is operative for the other of its load ranges.

20. In combination, a multi-load range weighing mechanism, a multi-load range indicating system having a rotatable indicating element, means for rendering the load ranges of the indicating system selectively operable including a load graduated dial having a plurality of sets of numbered load'graduations and a mask having a series of openings adapted to uncover the graduations of only one set of graduations or the other, means for angularly moving said dial to adjust the same relative to said mask to eifect a predetermined positioning of said indicating element relative to the mask openings in accordance with the load range at which it is desired to operate the weighing mechanism, and means for also rotating said indicating element to efiect a predetermined relation between the indicating system and the load graduations.

. 21. In combination, a multi-load range weighing system, a multi-load range indicating system having a dial provided with a plurality of sets of load range graduations angular-1y ofiset with respect to each other and each load range having its own zero graduation, a load indicating pointer actuated by said weighing system, means foradjusting the zero position of one load range by adjusting one range of the load weighing mechanism whereby the pointer is adjusted to its zero graduation, and means for adjusting the zero position of the other range of the indicating system by moving the dial relative to the pointer.

22. In combination, a multi-ioad range indicating system having a dial provided with a plurality of sets of load range graduations each having its own zero graduation offset from each other, a load indicating member, a mask for covering one set or the other of said graduations, means operatively connected to said dial forshiiting the mask relative thereto to render said sets of graduations selectively operative, and means fOr moving the dial and mask together as a, unit with said operative connection for establishing a zero position of one of said sets of graduations.

23. The combination set forth in claim 22 further characterized, by the provision of a midtiload weighing system, means for changing the load range of said weighing system, and means for connecting said load changing means with said mask shifting means including a flexible connection between the mask shifting means and the range changing means of the weighing system.

24. In combination, a Bourdon tube, on air operated servo-motor having a movable portion, an air jet and baliie controlled by said tube for controlling air pressure in said servo-motor, a rod and extensible means interposed between and connected to said servo-motor and said Bourdon tube, and a relatively stationary bracket having at least three radially disposed roller bearings for engaging and axially guiding said rod.

25.111 combination, a plurality of condition responsive means respectively adapted for different ranges of operation, a plurality of sets of springs oi? difl'erent degrees of flexibility, each of said responsive means respectively having connection with said sets; of springs, air controlled power means common to'said plurality 0! se of springs and operative to resist movement of said responsive means, said power means acting simultaneously on all of said sets of springs during each range of operation, a multi-range in,

(heating mechanism operated by said power means, and means for adjusting the Zero relation between the weighing mechanism and indicating means for each of said ranges.

26. In combination, a plurality of pressure responsive tubes operable for difierent ranges, a plurality of Sets of springs of difierent degrees of flexibility, one set being for one of said responsive means and another set for another of said responsive means, power means Common to said plurality of sets of springs and operative to resist movement of said tubes, jet and indie elements associated with each of said tubes so as to be respectively operated by the same, said power means acting simultaneously onvall of said sets of springs during each range of operation, a multi-load range indicating mechanism operated by said power means, and means for adjusting a zero relation between the weighing mechanism and indicating means including means for relatively adjusting said jet=bafie elevmerits thereby to operate said servo-motor and cause the indicating mechanism to be adjusted until the zero position is obtained.

2'7. In combination, amechanism having a pinrality of. condition responsive means respectively adapted for different ranges of operation, a plurality of sets of springs connected respectively to said plurality of responsive means, air controlled power means common to said plurality of sets of springs and respectively operative to resist movement of said plurality of said responsive means respectively; a device operated by said power means; and shifting means for rendering said power means responsive to one or another of said condition responsive means while maintaining said mechanism continuously. subject to the responsive condition.

28. In combination, load responsive means, and means for transmitting movement in accordance with said load responsive means including a rotatable worm wheel and a screw threaded rod tangentially engageable therewith so as to be moved axially upon rotation of said worm wheel and said threaded rod being axially adjustable by rotating the rod thereby to move the same tangentially relative to the worm wheel and bring rod threads into engagement with difierent worm gear teeth.

' MALCOLM C. TATE. 

